the buyer's fee is unlikely to be deductible.
Likely: if the 1099-MISC is the "hammer price", then the cost basis is the same as the "hammer price" - the buyer paid the buyer's fee and it's not in the 1099-MiSC. Not deductible since you did not pay it.
Possible, but unlikely: if the 1099-MISC is the "hammer price" + the buyer's commission. then the cost basis is the same as the sum of these two components. - the market value is presumed to include the buyer's commission, but that is the same as the market value on the date of death.
